Ignition distributor



Oct. 12, 1965 s uc 3,211,140

IGNITION DISTRIBUTOR Filed D60. 26, 1963 3 Sheets-Sheet 1 TAU/3A5 ATTORNEY Oct. 12, 1965 T. E. STUCK 3,211,140

IGNITION DISTRIBUTOR Filed Dec. 26, 1963 3 Sheets-Sheet 2 7790/14/15 4-. STUCK INVENTOR.

bb IM S7 ATTORNEY Oct. 12, 1965 T. E. STUCK 3,211,140

IGNITION DISTRIBUTOR Filed Dec. 26, 1965 3 Sheets-Sheet 3 THO/M45 E. 5 TUCK INVENTOR JT'TOR/VEY United States Patent 3,211,140 IGNITION DISTRIBUTOR Thomas E. Stuck, Roseville, Mich., assigmor to Holley Carburetor Company, Warren, Mich., a corporation of Michigan Filed Dec. 26, 1963, Ser. No. 333,360 11 Claims. (CL 123-149) This invention relates generally to ignition systems for internal combustion engines, and more particularly to a method and means for retrofitting a breaker contactcontrolled system to provide a pulse generator type semiconductor-controlled system.

The most common ignition system for an internal combustion engine includes an ignition coil and a socalled ignition distributor, the latter comprising a housing containing a set of breaker contacts operated by a multi-lobed cam driven by the distributor shaft so that opening of the contacts induces a relatively high voltage in the primary winding of the ignition coil. Such an ignition distributor is shown in Larges et al. 3,062,929.

One main problem with the above type of igition system is that arcing at the breaker contacts results in their deterioration so that they must be periodically replaced. To cope with this problem, ignition systems have been proposed wherein switching of the primary coil current is accomplished by a semiconductor device such as a transistor, rather than by a set of breaker contacts. In such systems, the transistor must be pulsed or triggered so that its switching function is accomplished in proper timed relation to the operation of the engine. While most of these proposed systems employ the prior breaker contacts to pulse the semiconductor, a more desirable system is to completely eliminate the breaker contacts and to substitute therefor a pulse generator having only one moving part, a so-called pulse wheel, as shown by Johnson 2,852,589.

It is believed that a novel and advantageous approach is to retrofit existing breaker contact-controlled ignition systems in a manner such that the ignition distributor unit thereof serves as the pulse generator. To accomplish this retrofit, it may be necessary to convert the cam of the existing distributor to a pulse wheel having more discrete projections than the lobes on the cam so as to produce voltage pulses of proper magnitude and shape, as proposed in US. application Serial No. 312,535, entitled Ignition Distributor and filed on September 30, 1963 in the names of Kalin S. Johnson and Philip V. Eshelman.

While the above referenced application discloses novel and inexpensive structure for converting a Larges type cam to a pulse wheel, the specific structure proposed therein cannot conveniently be employed to retrofit a distributor such as that shown by Hartzell et al. 2,769,047 wherein the cam has secured to the upper end thereof a centrifugal weight support plate. The obvious reason for this is that the support plate prevents applying the proposed retrofit structure over the cam, at least without removing the cam and the shaft on which itis mounted from the distributor housing.

Accordingly, an object of this invention is to provide a retrofit type pulse wheel assembly that will produce more suitable voltage signals than the distributor cam,

3,211,140 Patented Oct. 12, 1965 that has novel means for properly locating and rigidly securing the same to the hardened cam so as to prevent any shifting thereof in use and that can be applied to the type of cam having structure attached thereto preventing the application of a pulse wheel assembly over the free end thereof.

Another object of the invention is to provide such a pulse wheel assembly that is easy to manufacture and to assemble on a distributor cam, possibly without removing the distributor from the engine and certainly without removing the cam from the distributor.

Other objects and advantages of the invention will become more apparent when reference is made to the following specification and accompanying illustrations wherein:

FIGURE 1 is a schematic illustration of a semiconductor-controlled magnetically-pulsed ignition system;

FIGURE 2 is a plan view of a prior art distributor generally of the type shown by Hartzell et al. 2,769,047 and retrofitted in accordance with the invention for use in the system shown in FIGURE 1;

FIGURE 3 is an enlarged plan view of the pulse wheel assembly shown in FIGURE 2, the assembly being opened up and ready for mounting on the cam;

FIGURE 4 is a side elevational view of the assembly, as viewed from line 44 of FIGURE 3;

FIGURE 5 is a cross sectional view taken on the plane of line 5-5 of FIGURE 3 and looking in the direction of the arrows, after the FIGURE 3 assembly has been placed on the cam and before it is locked;

FIGURE 6 is a view similar to FIGURE 5, but illustrating the pulse wheel assembly in the locked condition;

FIGURE 7 is an enlarged plan view of one of the elements making up the assembly shown by FIGURES 2-6;

FIGURE 8 is an enlarged cross sectional view taken on the plane of line 88 of FIGURE 7 and looking in the direction of the arrows;

FIGURE 9 is an enlarged plan view of another element of the assembly shown by FIGURES 3-6.

Referring now to the drawings in greater detail, FIG- URE 1 illustrates schematically a typical transistor-controlled ignition system 10, including the usual battery 12, ignition switch 14, ignition coil 16 having a primary winding 18 and a secondary winding 20, rotor 22 and distributor cap terminals 24, a spark plug 26 of which there would be one for each engine cylinder, a pulse generator 28 including a pulse wheel 30 and a magnetic pick-up 32, and a pulse amplifier and switching unit 34. Such a system is generally familiar to those versed in the ignition art.

FIGURE 2 illustrates a prior art distributor which is generally similar to that shown by Hartzell et al. but having the rotor and cap removed and the cam cut off below the centrifugal weight support plate. Additionally, the distributor has been retrofitted in accordance with the invention to provide a pulse generator 28 for use in the ignition system shown by FIGURE 1. The distributor includes a housing 36 having an engine driven shaft 38 extending therethrough and through the movable breaker plate 39 and a cam 40 formed or fitted on the shaft, the cam having the same number of lobes 42 as there are cylinders on the engine.

By'reference to Hartzell et al. it will be observed in FIGURE 2 that the prior art breaker contacts and condenser have been removed from the breaker plate 39. The pulse generator 28, which serves the same general purpose as the pulse generator in Johnson 2,852,589, comprises generally a pulse wheel assembly 44 applied to and secured to the distributor cam 40 and the magnetic pick-up device 32. Since it forms no part of this invention, it is suflicient to say that the latter device includes a coil 46 wound around a magnetized core 48 secured to a bracket 5 that :may be adjustably mounted either directly on the breaker plate 39 in the same manner as the replaced breaker contacts or on the adapter plate 52 which is in turn secured to the breaker plate 39.

As in the case of most prior art distributor cams, the cam 40 is usually hardened and ground. It rotates at relativelyhigh speeds, and lubricating oil and grease accumulate on its surface. For these reasons, the pulse wheel assembly 44 must include means for properly locating and securing itto the cam so that it will not loosen and shift during operation "of'the pulse generator 28. Furthermore, since it'is to be mounted on a Hartzell et a1. type cam, the assembly '44 must be formed so that it can be opened up and applied to the cam horizontally or from the sidethereof, rather from the top thereof, and then closed up and locked.

The specific pulse wheel assembly embodying the invention is illustrated in greater detail in FIGURES 3-9. It can be seen that the assembly 44 comprises a generally "cylindrical body having an axial opening 46 adapted to receive the 'cam 40, the body being formed by properly stacking a plurality of thicker pulse wheel members 48, thinner locking members 50 and wider locating members 52. However, before discussing the structure of the assembly 44, the-structures of the individual pulse wheel, locking and locating members will be described. In this discussion, it should be understood that the assembly 44 must be opened, applied to the cam 40 from the side 'thereofand then closed around the cam; thus, the various members 48, 50 and 52referredto above are generally "semi-circular so that two identical members can be arranged to form asplit ring. Appropriate rings are then properly stacked and held together by screws54. By removing some of the screws, the assembly can be opened up, applied to the-side of the cam and closed; the screws can then be replaced andthe entire assembly tightened up.

One of the locking members 50 is illustrated in FIG U-RES"lfand fijand itis apparentthat this member may be inexpensively formed by stamping the same from relatively thin-magnetically permeable sheet metal. The inner periphery of themem ber 50 is formed with straight edges 56 adapted to engage half of the cam 40, which in this particular instance is an octagonal cam for aneight cylinder engine. The straight edges 56 may join ona radius con- "forming to the radius of a lobe 42 of the cam. Two of the straight edges 56 are originallyformed with the projections 58 shown in dotted lines. The member 50 may then be shearedat'the'ehds of'the projections 58 and the resulting tabs 60 bent upwardly, as shown inFIGURE 8, so that the tabs do notinitially interfere with the cam. The outer periphery of the member 50 is formed with projections 62 that are positioned opposite the cam lobes 42 when the member 50 is applied to the cam 40, and a circular'opening'64 adapted to receive a screw 54 is providedat eachsuch projection. It will thus be seen that when two of'the members 50 shown by FIGURE 7 are arranged to form a ring, there will be eight projections 62, :one for'each cam lobe '42, eight screw holes 54 and four locking tabs 60, which if bent back down into the plane of the ring will interfere with or engage the cam surfaces.

7 FIGURES illustrates one of the pulse wheel members 48. -It'will be apparent that'this member may also be *formed by stamping, just as in the case of the locking -me'mber '50. -Its-shape'is identical to that of the locking member 50 except that it is not formed with the locking tab 60. Instead, a notch 66 is formed at each edge 56 corresponding to the edge 56 of a locking member 50 on which a locking tab 60 is formed. The notches 66 are slightly longer than the width of the locking tabs 60 so that the tabs, when in the bent-up position, are received in the notches. As seen in FIGURE 5, the back edges 68 of the notches are positioned so that they will bend the tabs 60 back into the plane of the locking members 50 when the assembly 44 is tightened. As in the case of the locking members 50, two pulse wheel members 48 are arranged to form a split ring so that the ring includes eight projections 62, eight screw holes 64 and four notches 66.

The locating members 52 are shown as the top elements in the FIGURE 3 plan view, which is enlarged to a lesser degree than FIGURES 7-9. It can be seen that two of the locating members are arranged to form a split ring which also includes eight projections 62 and eight screw holes 64. However, the inner periphery '70 of the ring is circular rather than octagonal, and it contains no slots or tabs. It will also be noticed that these positioning members are slightly wider than the other two members so that they extend over the axial octagonal passage 46 through the assembly 40, thus providing a shoulder 72 to engage the top surface of the cam 40 so as to properly position the assembly 44 on the cam.

FIGURE 3 isa plan view of the assembly 44 in the opened-up condition and ready for application of the assembly'to the cam 40 from the side thereof, and FIG- URE 4 is an elevational view of the opened-up assembly 44. From these two views, it can be seen that the assembly -is made up by stacking alternate rings of pulse wheel 48 andlocking membersSl), with a ring of locating members 52 at the top of the stack. The members are arranged so that the projections 62 and the screw holes 64 are aligned, and four screws 54 are inserted throughthe appropriate screw holes, the holes 64 in the Ipulse wheel member 48 at the bottom of the stack being threaded to cooperate with the threads of the screws 54.

With the proper four screws loosely assembled, the

'top locating member 52 and the bottom pulse wheel member 48 on the left hand side-of the assembly, as viewed in FIGURES 3 and 4, maybe swung outwardly away from their dotted line position at the bottom of FIGURE 3; likewise, .at the right hand side of the assembly 44, allof the members between the top locating member 52 and the bottom pulse wheel member 48 can be swung outwardly from their .dotted line position at the bottom of FIGURE 3.

After the loose assembly 44is applied .to the cam,

the eleme ntsthereof will be'in aposition'shown by FIG- URE 5. That is, the engagement (of the back edges 68 of the notches 66 with the adjacent upturned tabs 60 will cause the various members toremain spaced from one another. Since the ta'bs'a're'still turned upwardly,

they do not interfere with the application of .the assembly to the'cam.

FIGURE 6. 68 of the notches 66 in the pulse wheel members 48 The outwardly turned members are then swung inwardly to their dotted line positions in FIGURE 3, after whichthe remaining four screws 54 are inserted in the screw holes =64 and allof the screws 54 are tightened down to draw the assembly 44 together, 'asshown in In this locked condition, the back edges have forcedthe tabs 60 back'down into the plane of the locking members 50 thereby jamming the free ends of lar design show'n, four tabs 60 are provided on the locking members 50, and four notches 66 are provided in the pulse wheel members 48 to receive the tabs in the loose condition shown by FIGURE 5. Obviously, different configurations would be provided for four and six cylinder applications, and other modifications may be made within the scope of the invention.

It is apparent that the laminated type pulse wheel assembly 44 shown is adapted to be inexpensively manufactured and very easily assembled and that effective means are provided for locking the assembly 44 on a cam 40 having hard smooth surfaces. Heat and the presence of lubricating oil cannot deteriorate the assembly or cause it to loosen. An assembly of this type can be easily made for any existing distributor cam, and retrofit of any prior art distributor, even the Hartzell et a1. type, can be accomplished by any unskilled person without removing the shaft 38 from the disrtibutor and without having to resort to any special tools or equipment.

Although but one embodiment of the invention has been disclosed, it is apparent that other modifications are possible within the scope of the appended claims.

What I claim as my invention is:

1. A device for converting an ignition distributor having a multi-lobe cam mounted on the distributor shaft and adapted to open and close a set of breaker contacts to a distributor having a pulse wheel driven by the distributor shaft, said device comprising a generally cylindri cal body having discrete equally spaced magnetically permeable projections extending radially from the outer surface thereof, said body having an axial opening conforming closely to the shape of said cam and adapting the same to be fitted on said cam, one end of said body having portions extending over said opening to provide shoulders for engaging the top of said cam and thereby positioning said body on said cam, the inner surfaces of said body at said opening having means for frictionally engaging the exterior surface of said cam, said body being constructed to provide a hinge enabling the same to be opened and applied to said cam from the side thereof.

2. A device such as that recited in claim 1, said device being constructed by stacking and clamping together a plurality of suitably formed arcuate members.

3. A device such as that recited in claim 2, wherein said engaging means comprises tabs extending from the inner periphery and bent out of the plane of some of said members, said tabs being such that clamping said members together causes said tabs to be bent back into said plane whereby the free ends thereof frictionally engage said cam.

4. A device for converting an ignition distributor having a multi-lobe cam mounted on the distributor shaft and adapted to open and close a set of breaker contacts to a distributor having a pulse wheel driven by the distributor shaft, said device comprising a hollow generallycylindrical body having discrete equally-spaced magnetically-permeable portions extending radially from the outer surface thereof, said body having means enabling the same to be opened and applied to said cam from the side rather than from the ends thereof, means on said body for gripping said cam, means formed at one end of said body for properly positioning the same on said cam, means for securing the opened portions of said body together after portion-s have been closed around said cam, said securing means cooperating with said engaging means in a manner to cause said gripping means to grip said cam.

5. A device for converting an ignition distributor having a multi-lobe cam mounted on the distributor shaft and adapted to open and close a set of breaker contacts to a distributor having a pulse Wheel driven by the distributor shaft, said device comprising a generally cylindrical body having discrete equally-spaced magneticallypermeable projections extending radially from the outer surface thereof, there being the same number of projections as there are lobes on said cam, said body having an axial opening conforming closely to the shape of said cam and adapting the same to be fitted on said cam, one end of said body having portions extending over said opening to provide shoulders for engaging the top of said cam and thereby positioning said body on said cam, the inner surfaces of said body at said opening having means for frictionally engaging the exterior surface of said cam, said body having means for opening the same in a direction transverse to the axis thereof.

6. A device for converting an ignition distributor having a multi-lobe cam mounted on the distributor shaft and adapted to open and close a set of breaker contacts to a distributor having a pulse wheel driven by the distributor shaft, said device comprising a generally cylindrical body formed from a stack of generally arcuate plates and having discrete equally-spaced magnetically-permeable projections extending radially from the outer surface thereof, there being the same number of projections as there are lobes on said cam, said body having an axial opening conforming closely to the shape of said cam and adapting the same to be fitted on said cam, one end of said body having portions extending over said opening to provide shoulders for engaging the top of said cam and thereby positioning said body on said cam, the inner surfaces of said body at said opening having means for frictionally engaging the exterior surface of said cam.

7. A pulse wheel for a magnetically-pulsed, semiconductor-controlled type internal combustion engine ignition system, said pulse wheel comprising an ignition distributor shaft, said shaft having formed thereon a cam having the same number of lobes as there are cylinders in said engine, and a retrofit pulse wheel assembly mounted on said cam, said assembly comprising a generally cylindrical body formed by properly stacking a plurality of generally-similar arcuate members, a top member of said assembly having inwardly extending portions for engaging the top of said cam and thereby positioning said assembly with respect to the axis of said cam, some of said arcuate members having inwardly extending tabs bent out of the plane thereof, said tabs being straightened so that they grip the outer surfaces of said cam when said arcuate members are clamped together, and means for clamping said members together.

8. An element for converting an ignition distributor having a multi-lobe cam mounted on a distributor shaft and adapted to open and close a set of breaker contacts to a distributor having a pulse wheel driven by the dis tributor shaft, said element comprising a relatively thin arcuate member having an inner periphery generally conforming to the shape of a portion of said cam, at least one tab extending inwardly from the inner periphery of said element and bent out of the plane thereof to the extent that the projection of the free end of said bent tab lies substantially along said inner periphery, the free end of said tab when bent back into the plane of said element extending inwardly beyond said inner periphery, the outer periphery of said element being formed with equally spaced discrete projections, and an opening adapted to receive a screw formed in said element adj acent each of said projections.

9. An element for converting an ignition distributor having a multi-lobe cam mounted on a distributor shaft and adapted to open and close a set of breaker contacts to a distributor having a pulse wheel driven by the dis tributor shaft, said element comprising a relatively thin arcuate member having an inner periphery generally conforming to the shape of a portion of said cam, the outer periphery of said element being formed with equallyspaced discrete projections, an opening formed adjacent each projection for receiving a screw, the inner periphery of said element being formed with at least one notch.

10. A device for converting an ignition distributor having a multi-lobe cam provided on the distributor shaft and adapted to open and close a set of breaker contacts to a distributor having-a pulse wheel driven by the distributor shaft, said device comprising a body having'discrete equallyspaced -magnetically permeable elements near the outer :periphery thereof, said body having a cavity with means adapting the same to be fit on said cam in a manner so that rotation between said body and said cam is prevented, andsaid body being consrtucted in a manner so as to be :openable and applied to said cam from the side rather than axially thereof.

11. A device for converting an ignition distributor havinga multi-lobe cam provided on the distributor shaft and adapted to open and close a set of breaker contacts to a distributor having a pulse wheel driven by the discam in a manner so that rotation between said body and said cam is prevented, said body being constructed ,in a manner so that .it may be opened and applied to said -ca1n.fro.rn-.the :side rather than axially :thereof.

No references cited.

RICHARD -B. WILKINSON, Primary Examiner. 

1. A DEVICE FOR CONVERTING AN IGNITION DISTRIBUTOR HAVING A MULTI-LOBE CAM MOUNTED ON THE DISTRIBUTOR SHAFT AND ADAPTED TO OPEN AND CLOSE A SET OF BREAKER CONTACTS TO A DISTRIBUTOR HAVING A PULSE WHEEL DRIVEN BY THE DISTRIBUTOR SHAFT, SAID DEVICE COMPRISING A GENERALLY CYLINDRICAL BODY HAVING DISCRETE EQUALLY SPACED MAGNETICALLY PERMEABLE PROJECTIONS EXTENDING READIALLY FROM THE OUTER SURFACE THEREOF, SAID BODY HAVING AN AXIAL OPENING CONFORMING CLOSELY TO THE SHAPE OF SAID CAM AND ADAPTING THE SAME TO BE FITTED ON SAID CAM, ONE END OF SAID BODY HAVING PORTIONS EXTENDING OVER SAID OPENING TO PROVIDE SHOULDERS FOR ENGAGING THE TOP OF SAID CAM AND THEREBY POSITIONING SAID BODY ON SAID CAM, THE INNER SURFACES OF SAID BODY AT SAID OPENING HAVING MEANS FOR FRICTIONALLY ENGAGING THE EXTERIOR SURFACE OF SAID CAM, SAID BODY BEING CONSTRUCTED TO PROVIDE A HINGE ENABLING THE SAME TO BE OPENED AND APPLIED TO SAID CAM FROM THE SIDE THEREOF. 